An ultrasonic diagnostic apparatus is designed to emit ultrasonic pulses generated by ultrasonic transducers disposed in an ultrasonic probe into an object to be examined. The ultrasonic diagnostic apparatus receives reflected ultrasound or signals produced due to differences in acoustic impedance among the tissues of the object. The ultrasonic diagnostic apparatus displays image data on a monitor, which is generated based on received signals corresponding to the reflected ultrasound. This diagnostic method allows easy observation of real-time two-dimensional images by simple operation of only bringing the ultrasonic probe into contact with the body surface, and it is widely used for functional diagnosis or morphological diagnosis of various organs in a living body. Ultrasonic diagnostic method, which obtains information by using reflected ultrasound from tissue or blood cells in the living body, have rapidly progressed along with two great technical developments of an ultrasonic reflection method and an ultrasonic Doppler method. And B-mode images and color Doppler images obtained by these techniques have become indispensable to recent ultrasonic image diagnosis.
On the other hand, a Doppler spectrum method and an M-mode method are available as a method of obtaining information of blood flow and moving function of heart wall in the object to be examined with quantitatively and sufficient accuracy.
In this Doppler spectrum method, ultrasonic transmission/reception is performed with respect to the same region of the object at predetermined intervals, and Doppler signals are detected by performing quadrature phase detection for reflected ultrasound from moving reflectors such as blood cells. In the quadrature phase detection, a reference signal is used which has a frequency almost equal to the resonance frequency of the ultrasonic transducers. A Doppler signal from a desired area (hereinafter mentioned as the “region of interest (ROI)”) is extracted from these Doppler signals by using a range gate, and Doppler spectrum data is generated by FFT (fast Fourier transform)-analyzing the extracted Doppler signal.
According to such a sequence, Doppler spectrum are continuously generated with respect to the Doppler signal obtained from the ROI in the object, and a plurality of Doppler spectrum data are sequentially arrayed to generate Doppler spectrum data. The Doppler spectrum data obtained by this ultrasonic Doppler method is generally displayed with a ordinate representing frequency, a abscissa representing time, and the power (intensity) of each frequency component being represented by a luminance (gray level). Various kinds of diagnosis parameters are measured on the basis of this Doppler spectrum data.
In the M-mode method, B-mode data are obtained by repeating ultrasound transmission to and ultrasound reception from a predetermined direction, and a plurality of B-mode data are sequentially arrayed to generate M-mode data. The M-mode data is displayed with an ordinate representing distance between the ultrasonic probe and reflectors, an abscissa representing time, and the reflective intensity of reflectors being represented by a luminance (gray level).
Usually, a position of the range gate which determines a collection position of Doppler spectrum data and a collection direction of M-mode data are set under B-mode image observation or colored Doppler image observation. A marker which shows the collection position and the collection direction are indicated on these images.
On the other hand, as a method of displaying Doppler spectrum data and M-mode data (hereinafter mentioned as the “time-series data”) on the monitor, which has limited display width, a scroll method and a moving bar method are proposed. In the scroll method, time-series data are shifted in a direction of time-axis one by one, and in the moving bar method, a cursor perpendicular to the time-axis is moved in the direction of the time-axis, and time-series data is updated to the newest one at this cursor position.
A setup of the collection position of time-series data is performed under observation of B-mode image data or colored Doppler image data (hereinafter mentioned as the “image data”) obtained in parallel with the time-series data, as described in Japanese Patent Publication (Kokai) No. 2004-73287, for example, and image data and time-series data are displayed simultaneously on the monitor.
According to a display method of image data and time-series data for setting the ROI described in this patent Publication, a display format (hereinafter mentioned as the “Left/Right display format”) is used which displays image data and time-series data in a left/right direction and side by side. By applying this display format, display of comparatively large image data is possible and the ROI can be set up correctly.
However, when displaying time-series data obtained from a desired ROI as freeze data and measuring various diagnostic parameters using the time-series data are carried out, the time-series data generated based on the Left/Right display format can not show a direction of time-axis broadly, and the measurement of diagnostic parameter is difficult. For this reason, in the measurement of diagnostic parameters, for example, a display format (hereinafter mentioned as “Up/Down display format”) which displays image data and time-series data in a vertical direction and side by side or a display format which displays only time-series data are used. By using these display formats, wide range time-series data can be displayed in the direction of the time-axis.
That is, when an operator measures diagnostic parameters using the time-series data which is displayed as freeze data, he needs to carry out a switching operation to a suitable display format. Especially, when a dynamic image display mode for setting the ROI and a freeze image display mode for measuring diagnostic parameters are repeated one after the other, manual change of the display format by the operator has become one of factors which reduce diagnostic efficiency remarkably.